Penn Engineering researchers have created a chip that surpasses the security and reliability of existing quantum communications hardware. Their technology communicates within “qudits”, doubling the quantum information space of any previous embedded laser.
Liang Feng, a professor in the Departments of Materials Science and Engineering (MSE) and Electrical Systems and Engineering (ESE), MSE postdoctoral fellow Zhifeng Zhang, and ESE Ph.D. Student Haoqi Zhao presented the technology in a recently published study. Nature. The group worked in collaboration with scientists from the Polytechnic University of Milan, the Interdisciplinary Institute for Physics and Complex Systems, Duke University, and the City University of New York (CUNY).
Beats, cubits and qudits
State-of-the-art quantum devices use qubits, while non-quantum chips store, transmit and compute data using bits. Bits can be 1 or 0, while qubits are digital information units that can be 1 and 0 at the same time. In quantum mechanics, this state of simultaneity is called “superposition”.
A quantum bit in a superposition state of more than two levels is called a qudit to indicate these additional dimensions.
“In classical communication,” says Feng, “a laser can emit a pulse that is coded as a 1 or a 0. These pulses can easily be cloned by an interceptor who wants to steal information, and are therefore not very secure. In quantum communication with qubits, a Pulse 1′ “It can have any superposition state from 0 to 0. Superposition does this so that the quantum pulse cannot be copied. Unlike algorithmic encryption, which locks hackers out using complex mathematics, quantum cryptography is a physical system that keeps information secure.”
But qubits aren’t perfect. With only two layers of overlap, qubits have limited storage space and low interference tolerance.
Feng Lab’s four-level qubits provide significant advances in quantum cryptography by increasing the maximum secret key rate for information exchange from 1 bit per pulse to 2 bits per pulse. The device offers four levels of overlap and opens the door for further size increases.
“The biggest challenge,” says Zhang, “was the complexity and non-extensibility of the standard setup. We already knew how to build these four-level systems, but this required a laboratory and many different optical instruments to check all the relevant parameters. on a chip. And that’s exactly what we did.” Source
Source: Port Altele
